Should my boiler still run with zero water pressure?

[Len Clifton]

As the title really - we have a Worcester Greenstar 24i which was fitted in 2021. Still running fine for heating and hot water, yet the gauge reads zero. Engineer came out for the annual service and simply refilled it. I thought the rule was combi boilers wouldn’t run without 0.5 bar pressure? I didn’t get the chance to ask him.

[ARHarh]

It was probably right on the lower limit. You may want to keep an eye on the pressure as it shouldn't loose any.

[Len Clifton]

ARHarh said:

It was probably right on the lower limit. You may want to keep an eye on the pressure as it shouldn't loose any.

Haven’t filled it for a year, but I take your point, might have a leaky valve somewhere and we have a lot of radiators.

[ferret50]

My combi's 'loss of pressure' turned out to be a failed pressure vessel.....it's only money.....and now works properly again.

[outnumbered]

Len Clifton said:

Haven’t filled it for a year, but I take your point, might have a leaky valve somewhere and we have a lot of radiators.

We have a similar boiler, and have had a couple of occurrences of issues with the internal expansion vessel. Leaky air valve, and leaky pressure relief valve. They do run for a surprisingly long time in the red part of the dial, but eventually will start making very nasty banging noises... Have you checked for water coming out of the expansion overflow pipe ?

[andySC]

Most combi boilers have a low water pressure switch that’ll activate around 0.5-0.7 bar & throw up an error code & shut it down. Worcester Greenstar boilers don’t have this component & will run with nothing showing on the gauge. Now you’re aware there’s a loss of pressure it’s worth keeping an eye on things & if you are topping up regularly then give your guy a call. It could be the pressure has gradually reduced in between services & there’s not much amiss.

Edited by andySC on Wednesday 30th April 07:17

[Len Clifton]

andySC said:

Most combi boilers have a low water pressure switch that’ll activate around 0.5-0.7 bar & throw up an error code & shut it down. Worcester boilers don’t have this component & will run with nothing showing on the gauge. Now you’re aware there’s a loss of pressure it’s worth keeping an eye on things & if you are topping up regularly then give your guy a call. It could be the pressure has gradually reduced in between services & there’s not much amiss.

Thanks, this is the answer I was looking for. I thought all boilers had the low pressure lockout feature. Will be more vigilant.

[dhutch]

Len Clifton said:

Thanks, this is the answer I was looking for. I thought all boilers had the low pressure lockout feature. Will be more vigilant.

Our Viessmann is the same, no low pressure lockout.

[TwistingMyMelon]

Same for me, same boiler as OP

Ive just topped it up for the last 6 years